Distribution and genetic diversity of Vibrio vulnificus in Galveston Bay water and oysters

This study systematically investigated the distribution and genetic diversity of Vibrio vulnificus in Galveston Bay water and oysters. Samples were collected at five sampling sites from June 2000 to June 2001 for the enumeration and isolation of V. vulnificus. Biotypes and colonial morphotypes of 208 V. vulnificus isolates were determined. Randomly amplified polymorphic DNA (RAPD) PCR was used to characterize the genetic diversity of the V. vulnificus strains and partial 16S rDNA sequencing was performed to deduce additional information related to the population structure and molecular evolution of this species.; Seasonal distribution of V. vulnificus was observed. Highest numbers occurred during late spring and summer months and none were detected during winter months. Ninety-eight percent of the V. vulnificus strains were of opaque morphotype. The isolation of seven biotype 2 strains from both water and oyster samples indicates that the marine environment should be regarded as a reservoir and possible vehicle of transmission for V. vulnificus biotype 2.; Cluster analysis of RAPD PCR profiles revealed a great genetic diversity among the strains, with biotype I strains more heterogeneous than biotype 2 strains. The genetic diversity of V. vulnificus did not correlate with sampling location, source nor date of isolation except that the majority of March isolates grouped together in cluster 8. Temperature increases after March may contribute to the genetic diversity and shift in population structure of V. vulnicus in the Galveston Bay.; V. vulnificus was separated into two groups which correspond to two different partial 16S rDNA sequences: type A and type B. The relative abundance of the two types of V. vulnificus strains changed with the season. Identical partial 16S rDNA sequences were found among biotype 2 strains. The slight sequence differences among biotype 1 strains support the higher degree of heterogeneity within this biotype as revealed by RAPD PCR.; The results of this study demonstrate that Galveston Bay contains a seasonally variable and very diverse population of V. vulnificus strains. The dynamic nature of the population structure of this species provides new information about the ecology, molecular evolution of V. vulnificus in the natural environment.